1. Field of the Invention
The present invention relates to a multilayered ceramic capacitor, a mounting structure of a circuit board having thereon the multilayered ceramic capacitor, a packing unit for the multilayered ceramic capacitor.
2. Description of the Related Art
A multilayered ceramic capacitor, a multilayered chip electronic component, is a chip-type condenser commonly mounted on the printed circuit boards of various electronic products, such as image display devices including a liquid crystal display (LCD) and a plasma display panel (PDP), computers, personal digital assistants (PDAs), mobile phones, and the like, implementing charging and discharging of electricity therein.
Multilayered ceramic capacitors (MLCCs) may be used as components of various electronic products due to a small size, high capacitance, and ease of mountability.
A multilayered ceramic capacitor may have a structure in which a plurality of dielectric layers and a plurality of internal electrodes having different polarities and having the dielectric layers interposed therebetween are alternately laminated with each other.
Since the plurality of dielectric layers have both piezoelectric and electrostrictive properties, a piezoelectric phenomenon may occur, causing vibrations among the internal electrodes when AC or DC voltage is applied to the multilayered ceramic capacitor.
Such vibrations may be transferred through external electrodes of the multilayered ceramic capacitor to a printed circuit board on which the multilayered ceramic capacitor is mounted, and the entire printed circuit board may become an acoustic reflection surface generating sound from the vibrations.
The sound generated by the vibrations may correspond to an audible frequency within the range of 20 to 20000 Hz, and this vibrating sound, frequently causing an unpleasant feeling in people is known as acoustic noise.
In order to reduce acoustic noise, products in which a lower cover layer of the multilayered ceramic capacitor is enlarged have been researched.
Generally, equivalent series inductance (ESL) is proportional to the area of a current loop.
Therefore, as described above, the multilayered ceramic capacitor in which a lower cover layer is enlarged can partially reduce acoustic noise, but may have higher ESL as compared with products of the related art of which the lower cover layer is relatively thin.
The related art document below illustrates improvement in ESL, but fails to disclose a structure in which a lower cover layer includes an internal electrode.